Serious investigative journalism could be "killed off" by the privacy precedent set by Naomi Campbell's victory over the Mirror newspaper, a top media lawyer has warned.

Some of the country's biggest public scandals might never have been uncovered by journalists if the rules set by the judge today had been in place, according to Paul Gilbert, a media lawyer at London law firm Finers Stephens Innocent.

And he believes the ruling causes confusion about privacy and could lead celebrities to use the courts to attempt to gag the media.

Mr Gilbert said there was reason for concern at Ms Campbell's victory on counts of breach of confidence and unlawful invasion of privacy.

"The media needs to be very careful about what they reveal and where information comes from. Journalists will need to look very carefully at what the judge has found," he said.

"The Keith Vaz case, for instance, would not have been revealed if it weren't for some very thorough investigative journalism. The biggest fear is that this sort of journalism may be killed off."

"There is reason for concern. Journalists will have to look very careful at the reasons why Naomi Campbell won and be careful about the source of the information and have an ear as to whether what they are investigating is in the public interest."

The cases against Jeffrey Archer and Jonathan Aitken, built up through journalistic investigation, might also have never reached the conclusion they did had today's ruling been in place.

But Mr Gilbert said Mr Justice Morland's ruling will cause confusion - it flies in the face of a recent ruling over a footballer's courtroom battle with the People newspaper over a "kiss-and-tell" story about a top footballer.

Today's ruling could also lead to celebrities thinking that they can gag the media, he said.

"The judge has laid down markers for those things to be protected by a privacy law. But also he is saying that celebrities should not think they can come along and expect the court to help gag the media, or act as a spin doctor for what they do and do not want to allow into the press.

"But if you compare this ruling with the footballer decision there is some confusion about where we are.

"There is a world of difference between a 'kiss-and-tell' situation - where the right of the 'kiss-and-teller' to tell their story is weighed against the right of the celebrity to protect their privacy - and this ruling.

"The difference is that in Ms Campbell's case, the paper's information that she would be at the Narcotics Anonymous meeting came from a tip-off from a source.

"The editor of the Sunday People said his ruling proved we don't have a privacy law, but we do. And if newspapers thought, after that ruling, there was carte blanche to publish if it is the public interest, well, it is not as simple as that," said Mr Gilbert.

Two weeks' ago the court of appeal ruled that a judge had been wrong to ban the People from publishing interviews with two women who had affairs with a married Premiership footballer .

The millionaire player was ruled to be a public figure who had no right to block a newspaper's publication of "kiss-and-tell" stories about his infidelities.

Lord Woolf, the lord chief justice, said: "Ignoring, as one must, the literary quality of what it was proposed to publish, it is not self-evident that how a well-known premiership football player... chooses to spend his time off the football field does not have a modicum of public interest.

"Footballers are role models for young people and undesirable behaviour on their part can set an unfortunate example."

The footballer was "inevitably a figure in whom a section of the public and the media would be interested".